Systems and methods for display systems with dynamic power control

ABSTRACT

Methods and systems to dynamically adjust a voltage supply of a display are provided. Systems are provided to receive a digital data input indicative of an amount of luminance to be emitted from the display, to determine a desired supply voltage to supply to the display based on the received digital data, and to adjust an adjustable voltage supply according to the determined desired supply voltage. Furthermore, the methods and systems disclosed herein provide for dynamically separately controlling supply voltages supplied to distinct subsections of the display. Systems and methods are also provided for operating a display device in an idle mode by turning off subsections of the display that would otherwise be shown dark and thereby save energy required to program the subsections with display information.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/459,979, filed Aug. 14, 2014, now allowed, which is acontinuation-in-part and claims priority to U.S. patent application Ser.No. 13/474,131, dated May 17, 2012, now U.S. Pat. No. 9,134,825, whichclaims the benefit of U.S. Provisional Patent Application No.61/487,272, filed May 17, 2011, each of which is hereby incorporated byreference herein in its entirety.

FIELD OF THE INVENTION

The present invention generally relates to emissive displays, andparticularly to displays incorporating a dynamically adjustable powersupply adjusting a supply voltage based on the luminance of the display.

BACKGROUND

Currently, active matrix organic light emitting device (“AMOLED”)displays are being introduced. The advantages of such displays includelower power consumption, manufacturing flexibility and faster refreshrate over conventional liquid crystal displays. In contrast toconventional liquid crystal displays, there is no backlighting in anAMOLED display as each pixel consists of different colored OLEDsemitting light independently. Because no backlight is required, anAMOLED display generally consumes less power than a backlight display.

The OLEDs emit light based on current supplied through a drivetransistor. The drive transistor is typically a thin film transistor(TFT), and the current level through the drive transistor is dependenton a voltage applied to the gate terminal of the drive transistor. Somedisplays include capacitors within each pixel to be charged according toprogramming information and then apply the stored charge to the drivetransistor to control its current level. The power consumed in eachpixel at any instant is related to the current through the pixel and thevoltage across the pixel.

SUMMARY

Some embodiments of the present disclosure provide a system for drivinga display. The system can include a first plurality of pixel circuits, afirst plurality of supply lines, an adjustable voltage supply, and acontroller. The first plurality of pixel circuits can be arranged in anarray, and each of the first plurality of pixel circuits can include alight emitting device and a driving transistor for conveying a drivingcurrent through the light emitting device. Each of the first pluralityof supply lines can be associated with one or more of the firstplurality of pixel circuits. The first plurality of supply lines canprovide driving currents to the one or more of the first plurality ofpixel circuits associated therewith. The adjustable voltage supply canbe configured to provide a supply voltage to at least one of the firstplurality of supply lines. The controller can be for determining, basedon digital data indicative of an amount of luminance to be emitted fromthe first plurality of pixel circuits, an output level from theadjustable voltage supply to apply to the at least one of the firstplurality of supply lines. The output level can be sufficient to enablethe one or more of the first plurality of pixel circuits associated withthe at least one of the first plurality of supply lines to emit lightaccording to the digital data.

Some embodiments of the present disclosure provide a method of operatinga display. The method can include receiving digital data input;determining, based on the input, one of a plurality of supply voltagesto apply to the first plurality of pixels; and adjusting a voltage ofone or more supply voltage lines. The received digital data input can beindicative of an amount of luminance to be emitted from a firstplurality of pixels in the display. The one or more supply voltage linescan be associated with the first plurality of pixels, and can beadjusted according to the determined one of the plurality of supplyvoltages.

Some embodiments of the present disclosure provide a method of operatinga display. The method can include turning off a voltage supply lineassociated with a first portion of the display during an idle mode ofthe display while the first portion is set to a dark setting; andceasing programming of the first portion of the display.

The foregoing and additional aspects and embodiments of the presentinvention will be apparent to those of ordinary skill in the art in viewof the detailed description of various embodiments and/or aspects, whichis made with reference to the drawings, a brief description of which isprovided next.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other advantages of the invention will become apparentupon reading the following detailed description and upon reference tothe drawings.

FIG. 1A is a diagram of a display system incorporating an adjustablevoltage supply.

FIG. 1B is a circuit diagram of an exemplary pixel circuit showingvoltage levels across the drive transistor and the light emittingdevice.

FIG. 2 is a diagram of a display system incorporating an adjustablevoltage supply to separately adjust supply lines for a plurality ofsubsections of a display.

FIG. 3A illustrates a flow chart for an exemplary method of operating adisplay while decreasing the power consumption of the display.

FIG. 3B illustrates a flow chart for another exemplary method ofoperating a display.

FIG. 4 illustrates a flowchart for another exemplary method of operatinga display.

FIG. 5 illustrates an example screen capture of a display of a list ofemails and incorporating selectable features.

FIG. 6A is an example screen capture of a display menu with selectablefeatures.

FIG. 6B is another example screen capture of the screen shown in FIG.6A, but with an additional highlighted region shown.

FIG. 7 illustrates an example configuration for electrode patterning ofa display array where supply lines are separately adjustable.

FIG. 8 illustrates another example configuration for a pattern ofelectrodes in a display array where supply lines are separatelyadjustable.

FIG. 9 is a diagrammatic illustration of a display with segmented Vddfor power saving.

FIG. 10 is a block diagram of a standby mode with a display showingactive content.

FIG. 11 is a block diagram of a display module with multiple framebuffers for supporting active content during standby.

FIG. 12 is a block diagram of a display module with frame buffers and acontent generation module for supporting active content during standby.

While the invention is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and will be described in detail herein. Itshould be understood, however, that the invention is not intended to belimited to the particular forms disclosed. Rather, the invention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

FIG. 1A is a block diagram of an exemplary display system 100incorporating an adjustable voltage supply 140. The display system 100includes an address driver 120, a data driver 110, and a controller 130.The controller 130 receives digital data indicative of information to bedisplayed via the display system 100. The controller 130 sends datasignals 134 to the data driver 110, scheduling signals 132 to theaddress driver 120, and control signals 136 to the adjustable voltagesupply 140 to drive a display array to display the informationindicated. The display system 100 generally includes a display arraywith an array of pixels, such as the pixel 10, arranged in rows incolumns. The display array can include conductive and/or semi-conductiveelements formed (e.g., by a deposition process) on a display substrate,an encapsulation substrate (e.g., glass), or a combination ofsubstrates. Each of the pixels (e.g., the pixel 10) is individuallyprogrammable to emit light with individually programmable luminancevalues. The array of pixels thus comprise the display array (“displayscreen”) adapted to dynamically display information according to thedigital display data input to the controller 130. The display screen candisplay, for example, video information from a stream of video datareceived by the controller 130.

For illustrative purposes, the display system 100 in FIG. 1A isillustrated with a single pixel 10. It is understood that the displaysystem 100 can be implemented with a display screen that includes anarray of similar pixels, such as the pixel 10, and that the displayscreen is not limited to a particular number of rows and columns ofpixels. For example, the display system 100 can be implemented with adisplay array with a number of rows and columns of pixels commonlyavailable in displays for mobile devices, television displays, computermonitors, heads up displays, etc.

The pixel 10 is operated by a driving circuit (“pixel circuit”) thatincludes a driving transistor and a light emitting device. Hereinafterthe pixel 10 may refer to the pixel circuit. The light emitting devicecan optionally be an organic light emitting diode, but implementationsof the present disclosure apply to pixel circuits having otherelectroluminescence devices, including current-driven light emittingdevices. The driving transistor in the pixel 10 can optionally be ann-type or p-type thin-film transistor, but implementations of thepresent disclosure are not limited to pixel circuits having a particularpolarity of transistor or only to pixel circuits having thin-filmtransistors.

The pixel 10 is coupled to a select line 122, a first supply line 142, asecond supply line 144, a data line 114, and a monitor line 112. Theselect line 122 is provided by the address driver 120, and can beutilized to enable, for example, a programming operation of the pixel 10by activating a switch or transistor to allow the data line 114 toprogram the pixel 10. The data line 114 conveys programming informationfrom the data driver 110 to the pixel 10. For example, the data line 114can be utilized to apply a programming voltage or a programming currentto the pixel 10. The programming voltage/current can be at a levelsufficient to charge a capacitor within the pixel 10 such that the drivetransistor is operated to convey current through the light emittingdevice to emit light with a desired amount of luminance. The programmingvoltage (or programming current) supplied by the data driver 110 via thedata line 114 is generally related to the digital data received by thecontroller 130 by a relationship expressed as a formula and/or by alookup table that maps digital data values to programmingvoltage/current levels.

The programming voltage/current can be applied to the pixel 10 during aprogramming operation of the pixel 10 so as to charge a storage devicewithin the pixel 10, such as a capacitor. Following the programmingoperation, the pixel 10 can emit light with the desired amount ofluminance during an emission operation. For example, the storage devicein the pixel 10 can be charged during a programming operation to apply avoltage to one or more of a gate and/or source terminal of the drivetransistor during the emission operation. By applying the charge(“voltage”) on the capacitor to the gate and/or source of the drivetransistor, the conductance of the drive transistor is adjustedaccording to the current-voltage characteristics of the drivetransistor, and a current is conveyed through the light emitting deviceaccording to the voltage stored on the capacitor.

Generally, in the pixel 10, the driving current that is conveyed throughthe light emitting device by the driving transistor during the emissionoperation of the pixel 10 is a current that is supplied by the firstsupply line 142 and is drained to the second supply line 144. The firstsupply line 142 and the second supply line 144 are coupled to theadjustable voltage supply 140. The first supply line 142 can provide apositive supply voltage (e.g., the voltage commonly referred to incircuit design as “Vdd”) and the second supply line 144 can provide anegative supply voltage (e.g., the voltage commonly referred to incircuit design as “Vss”). In some embodiments of the present disclosure,one or the other of the supply lines 142, 144 are fixed at a groundvoltage or at another reference voltage, and need not be connected tothe adjustable voltage supply.

In some embodiments of the present disclosure, either the first supplyline 142, or the second supply line 144, or both are adjustable by theadjustable voltage supply 140 according to the control signals 136 fromthe controller 130. For example, the value of the positive supplyvoltage Vdd and/or the value of the negative supply voltage Vss can beadjusted by the adjustable voltage supply 140. The difference betweenthe voltages on the first supply line 142 and the second supply line 144influences the amount of power drawn by the pixel 10 during theprogramming operation of the pixel 10. Generally, the power required bythe pixel 10 during the emission phase of the pixel 10 is proportionalto (Vdd−Vss)×Idrive, where Idrive is the driving current conveyedthrough the driving transistor, and through the light emitting device,as previously described. Thus, by reducing the difference between Vddand Vss, the power required to drive the pixel 10 can be reduced. Thedifference between Vdd and Vss (“ΔV”) supplied to the pixel 10 can becontrolled (e.g., reduced) by adjusting the voltage on the first supplyline 142 and/or the second supply line 144.

FIG. 1B is a circuit diagram of an exemplary pixel circuit showingvoltage levels across a drive transistor 152 and a light emitting device154. The pixel circuit in FIG. 1B is provided for illustrative purposesonly to illustrate the series connection between the drive transistor152, the light emitting device 154 between the two voltage supply lines142, 144. Generally, the pixel circuit 10 shown in FIG. 1A can includean n-type or p-type drive transistor, and an arrangement of additionaltransistors and/or capacitors arranged to selectively connect to thedata line 114 for programming the pixel circuit 10 according to voltageprogramming and/or current programming information and charging one ormore capacitors within the pixel circuit to influence the conductance ofa drive transistor.

In the exemplary arrangement shown in FIG. 1B, the drive transistor 152is connected in series between the high voltage supply line 142 (“Vddline”) and the light emitting device 154. For example, the drivetransistor 152 can have a drain and source and the drain of the drivetransistor 152 can be connected to the high voltage supply line 142 andthe source of the drive transistor 152 can be connected to the lightemitting device 154. The light emitting device 154 is connected betweenthe drive transistor 152 and the low voltage supply line 144 (“Vssline”). For example, the light emitting device 154 can have an anode andcathode and the anode of the light emitting device 154 can be connectedto the drive transistor 152 and the cathode of the light emitting device154 can be connected to the low voltage supply line 144. The gateterminal of the drive transistor 152 is connected to a storage capacitor156. The storage capacitor 156 is configured to apply a voltage to thegate of the drive transistor 152 so as to influence the conductance ofthe drive transistor 152 such that the current conveyed through thelight emitting device 154 via the drive transistor 152 is controlled bythe voltage on the storage capacitor 156. The storage capacitor 156 isshown connected to a ground voltage, but can alternatively be connectedto the anode terminal of the light emitting device 154, one or the otherof the supply voltage lines 142, 144, a reference voltage, and/oranother stable voltage sufficient to allow the storage capacitor 154 tobe charged according to programming information and apply a voltage tothe drive transistor so as to influence the conductance of the drivetransistor 152.

FIG. 1B also includes a diagram showing the voltage across the pixelcircuit between the two voltage supply lines 142, 144. The total voltagedifference between the voltage supply lines 142, 144 supplied via theadjustable voltage supply 140 is given by Vdd^(supply)−Vss^(supply)=ΔV,or DV_(TOTAL)), where Vdd^(supply) and Vss^(supply) are the voltagesoutput from the adjustable voltage supply on the supply lines 142, 144.At the pixel circuit, the voltages on the voltage supply lines 142, 144are generally decreased/increased due to the resistive line lossesbetween the adjustable voltage supply 140 and the pixel circuit beingpowered. Thus, the voltage on the Vdd line 142 at the pixel circuitshown in FIG. 1B is Vdd^(supply)−(Vdd IR Drop). Similarly, the voltageon the Vss line 144 at the pixel circuit shown in FIG. 1B isVss^(supply)−(Vss IR Rise). The “IR Drop” and “IR Rise” refers to thevoltages resulting from resistive line losses, where “I” refers to thecurrent on the line and “R” refers to the line resistance. The voltageacross the light emitting device (which can optionally be an OLED) isshown as V_(OLED). The value of V_(OLED) generally depends on thecharacteristics of the light emitting device 154, the aging history ofthe light emitting device 154, and/or the current being conveyed throughthe light emitting device 154. In some examples, the value of V_(OLED)can increase with increasing drive current (i.e., increased luminance)and the increase can be compensated for by measuring and/or predictingthe increase based on measurements from the monitoring system 115 orbased on calibrated look-up tables stored in a memory 116 to mappredicted aging degradation to usage histories/profiles.

The voltage across the drive transistor 152 is shown as V_(DS), whereV_(DS) can refer to the “drain-source” voltage across the drivetransistor 152. In some embodiments, the value of voltage across thetransistor (e.g., the drain-source voltage V_(DS)) is sufficient to keepthe drive transistor 152 in the saturation mode of operation, because atsaturation the amount of current conveyed through a transistor issubstantially independent of the voltage across the transistor. Forexample, the drive transistor 152 can operate in the saturation modewhile V_(DS)>V_(GS)−Vth, where V_(GS) is the voltage between gate andsource terminals of the drive transistor 152 and Vth is the thresholdvoltage of the drive transistor 152. Thus, the value of VDS required tomaintain the drive transistor 152 in saturation mode is dependent on thevalues of VGS and the threshold voltage, Vth. The value of Vth canchange over time due to electrical degradation of the drive transistor152. Similar to the discussion of V_(OLED) above, the value of Vth canbe compensated for over time according to measured and/or predictedvalues based on, for example, measurements via the monitoring system 115and/or look-up tables stored in the memory 116 and mapped to usageprofiles/histories. Where the value of V_(DS) is greater than necessaryto set the drive transistor 152 in the saturated mode, the excessvoltage (i.e., the excess amount of V_(DS) still applied across thedrive transistor 152) is generally dissipated within the channel regionof the drive transistor 152 as heat energy. In some examples, excessiveheat generation in the channel region undesirably contributes todegradation of the drive transistor 152, and thus, the aging of thedisplay system 100.

Thus, in some examples, the values of Vdd^(supply) and/or Vss^(supply)are selected to provide a voltage across the drive transistor 152 (e.g.,the voltage V_(DS)) sufficient to set the drive transistor 152 in thesaturated mode. The required value of V_(DS) can be determined, at leastin part, according to the measured and/or predicted values of Vdd IRDrop, Vss IR Rise, V_(OLED), Vth. Additionally or alternatively, therequired value of V_(DS) can be determined, at least in part, accordingto the programming information for the pixel circuit, because theprogramming information influences the value of V_(Gs), because theluminance of the light emitting device 154 is generally related to thecurrent through the drive transistor 152, and the current through thedrive transistor 152 is regulated, at least in part, by V_(GS). Forexample, the current through the drive transistor (“I_(Ds)”) can be setaccording to the relation I_(DS)=β(V_(GS)−Vth)², where β is a variablecharacterizing the current-voltage behavior of the drive transistor 152,and can include gate oxide, aspect ratio, mobility, etc. of the drivetransistor 152. Thus, the value of V_(GS) is determined, at least inpart, according to the luminance output from pixel circuit, and thus isdetermined, at least in part, according to the programming informationfor the pixel circuit.

In some embodiments of the present disclosure, the controller 130analyzes the digital data indicating luminance values for the display todetermine an amount to adjust the voltage on the first supply 142 and/orthe second supply 144 such that the pixels in the display array willhave sufficient power to produce the desired amount of luminance. Insome embodiments, the controller 130 analyzes the digital data and/ormeasured, stored, and/or predicted degradation information for pixels inthe display (such as values of V_(OLED), Vth, etc.), and adjusts thevoltage on the first supply line 142 and/or the second supply line 144such that the pixels in the display array are each set in the saturatedcondition. In some examples, the controller 130 can analyze the incomingdigital data to determine the required values of ΔV_(TOTAL) to set eachpixel in the display system 100 in the saturated mode, and then thevalues of Vdd and/or Vss supplied via the adjustable voltage supply 140can be set according to the maximum required value of ΔV_(TOTAL) in thedisplay for each frame. By setting the value of DVTOTAL according to themaximum required value for each frame, rather than the maximum requiredvalue across all frames, the value of voltage across each pixel can beno greater than necessary on a frame-by-frame basis. Furthermore,because the pixels are all set in the saturated condition, there isgenerally no decrease in luminance, because the currents through thepixels are unaffected. Because the power through the display panel isset dependent on the product of voltage across each pixel and currentthrough each pixel, decreasing the voltage also decreases powerconsumption (and also decreases heat generation within the drivetransistor channel regions).

The controller 130 can be configured to advantageously calculate anoptimum magnitude of the difference between Vdd and Vss (“ΔV”) such thatthe power consumed by the display system 100 is reduced as much aspossible while still providing sufficient power to the pixels to producethe luminance values specified by the input data. The determination ofthe voltages to provide on the first supply line 142 and/or the secondsupply line 144 can be carried out in the controller 130 dynamically,such as on a frame-by-frame basis when the display system 100 isdisplaying video. The controller 130 can select a desired voltage toprovide on the supply lines 142, 144 by analyzing the input data todetermine, for example, the maximum luminance value to be emitted fromthe display. The controller 130 can also compute the total cumulativecurrent to be drawn by all the pixels in the display to determine atotal load placed on the adjustable voltage supply 140 during aparticular frame.

The controller 130 selects desired voltages to be provided via thesupply lines 142, 144 by using a formula and/or a look up table. Theselection of the desired voltages can be accomplished by firstcalculating an optimal voltage (e.g., an optimal level of ΔV). In someexamples, the adjustable voltage supply 140 can be configured to provideoutput voltages at a series of predetermined voltage levels (e.g., aseries of voltages separated by a resolution of the driver of theadjustable voltage supply 140). The controller 130 can optionally selectthe closest available value of ΔV_(TOTAL) by adjusting one or both ofthe supply lines 142, 144 to predetermined levels. In some examples, thecontroller 130 selects the predetermined levels of the supply lines 142,144 to select the next highest value of ΔV_(TOTAL) over the determinedoptimal value. The selection of the desired voltage can also beaccomplished by the controller 130 by determining, based on the digitalinput data, whether the total load to be drawn by the display and/or themaximum desired luminance value of the display are above or below a setof trigger values, or within a range specified by trigger values. Theset of trigger values, or the ranges specified between the triggervalues, can correspond to particular voltages provided by the adjustablevoltage supply 140.

In the system 100, the supply lines 142, 144 providing supply voltagesto the pixels in the display are coupled to the adjustable voltagesupply 140. The individual supply lines coupled to the adjustablevoltage supply 140 can be arranged along rows (or columns) of thedisplay such that each supply line supplies a supply voltage to pixelsin a common row (or column) of the display. Implementations can alsoprovide for each supply line to be shared by pixels in adjacent rows (orcolumns) of the display.

In implementations of the display system 100 incorporating a monitoringsystem 115, the pixel 10 is also coupled to a monitor line 112. Themonitor line 112 connects the pixel 10 to the monitor system 115. Themonitor system 115 can be integrated with the data driver 110, or can bea separate stand-alone system. In particular, the monitoring system 115can optionally be implemented by monitoring the current and/or voltageof the data line 114 during a monitoring operation of the pixel 10, andthe monitor line 112 can be entirely omitted. Additionally, the displaysystem 100 can be implemented without the monitoring system 115 or themonitor line 112. The monitor line 112 allows the monitoring system 115to measure a current or voltage associated with the pixel 10 and therebyextract information indicative of a degradation of the pixel 10. Forexample, the monitoring system 115 can extract, via the monitor line112, a current flowing through the drive transistor (e.g., the drivetransistor 152) within the pixel 10 and thereby determine, based on themeasured current and based on the voltages applied to the drivingtransistor during the measurement, a threshold voltage of the drivingtransistor or a shift thereof. The monitoring system 115 can alsoextract an operating voltage of the light emitting device (e.g., avoltage drop across the light emitting device while the light emittingdevice is operating to emit light, such as V_(OLED) across the lightemitting device 154). The monitoring system 115 can then communicate thesignals 134 to the controller 130 and/or the memory 116 to allow thedisplay system 100 to compensate for the extracted degradationinformation in subsequent programming and/or emission operations of thepixel 10. For example, once the degradation information is extracted,the programming information conveyed to the pixel 10 via the data line114 can be appropriate adjusted during a subsequent programming and/oremission operation of the pixel 10 such that the pixel 10 emits lightwith a desired amount of luminance that is independent of thedegradation of the pixel 10. It is specifically noted thatimplementations of the present disclosure can be realized with orwithout the monitoring system 115.

FIG. 2 is a diagram of a display system 200 incorporating an adjustablevoltage supply 240 to separately adjust supply lines (e.g., the supplylines 241, 242) for a plurality of subsections (e.g., the subsections211 to 216) of a display 210. The display system 200 also includes acontroller 230 for receiving digital data 232 and for controlling theadjustable voltage supply 240 via control signals 234. Similar in somerespects to the display described in connection with FIG. 1A, thedisplay 210 generally includes an array of pixels that are individuallyprogrammable to emit light with individually programmable luminancevalues according to information indicated by the digital data 232.However, the display 210 differs from the display screen previouslydescribed in that the display 210 includes a plurality of discretesubsections. The display 210 includes a first subsection 211, a secondsubsection 212, a third subsection 213, a fourth subsection 214, a fifthsubsection 215, and a sixth subsection 216. The subsections 211-216 canbe supplied with supply voltages that are distinct from one another. Forexample, the first subsection 211 is supplied with the first supplyvoltage Vdd₁ via the first supply line 241; the second subsection 212 issupplied with the second supply voltage Vdd₂ via the second supply line242; the sixth subsection 216 is supplied with the sixth supply voltageVdd₆ via the sixth supply line 243. Similarly, while not separatelyillustrated, the remaining subsections 213-215 are supplied withrespective, separately controllable supply voltages Vdd3, Vdd4, Vdd5 viarespective supply lines for each subsection. The supply lines (e.g., thesupply lines 241, 242, . . . , 243) corresponding to each subsection211-216 are each coupled to the adjustable voltage supply 240 and toterminals connected to the respective subsections (e.g., the terminals211 a, 211 b for the first subsection 211). The adjustable voltagesupply 240 is configured to separately, and simultaneously, providedistinct supply voltages to the respective subsections 211-216.

The first supply line 241 and the second supply line 242 in FIG. 2 arerelated, but separate from, the pixel-level supply lines 142 and 144illustrated in FIG. 1A. In particular, the first supply line 241 and thesecond supply line 242 are conductive lines that connect entire portions(i.e., subsections) of the display 210 to a supply voltage appropriateto the respective portion. The first display line 241 and the seconddisplay line 242 can each be electrically connected to a plurality ofindividual lines (“power rails”), akin to the supply lines 142 and 144illustrated in FIG. 1, that are then connected to individual pixelswithin the respective subsections 211-216.

The connection between the first supply line 241 and the plurality ofindividual lines in the first subsection 211 is illustrated symbolicallyby the first terminal 211 a and the second terminal 211 b. The firstterminal 211 a provides a point of coupling between the plurality ofpower rails, or positive voltage supply lines, that are connected to thepixels in the first subsection 211. The second terminal 211 b alsoprovides a point of coupling between the plurality of power rails thatare connected to the pixels in the first subsection 211, but from a sideof the display 210 opposite a side having the first terminal 211 a. Bycoupling the first supply line 241 to both terminals 211 a, 211 b, thepixels in the subsection 211 are advantageously less affected byvariations in the supply voltage across the subsection 211. Thus, theeffect of Vdd IR Drop discussed in connection with FIG. 1B can be lesssevere in the display system 200 than in other systems. However, thedisplays system 200 can be implemented with the power supply lines(e.g., the power supply lines 241, 242) connected to each respectivesubsection 211-216 via a single terminal (e.g., the first terminal 211a) rather than via two terminals. The remaining subsections 212 to 216can be connected to the adjustable voltage supply 240 via terminalssimilar to the terminals 211 a and 211 b described for the firstsubsection 211. For example, the second supply voltage Vdd₂ can bedelivered to power rails in the second subsection 212 via the terminals212 a, 212 b; and the sixth supply voltage Vdd₆ can be delivered topower rails in the sixth subsection 216 via the terminals 216 a, 216 b.

In operation of the display system 200, the controller 230 is adapted toreceive the digital data 232 and determine appropriate voltages toprovide to each subsection 211-216 based on the digital data 232 (andoptionally based on measured and/or predicted degradation informationfor the display). The controller 232 then sends the control signals 234to the adjustable voltage supply 240 to instruct the adjustable voltagesupply 240 to supply the appropriate voltages to the subsections211-216. The controller 230 can determine the appropriate supplyvoltages for each subsection in a manner similar to the description ofthe operation of the controller 130 and the adjustable voltage supply140 in connection with FIG. 1A, and can include calculating maximumluminance values for each subsection 211-216, total effective load foreach subsection 211-216, and the use of threshold values and/or rangesto select an appropriate voltage. Additionally or alternatively, thecontrol 230 can determine voltage levels required to set pixels in eachsubsection 211-216 in the saturated mode. In contrast to the displaysystem 100 in FIG. 1A, the controller 230 in FIG. 2 can separatelydetermine an appropriate voltage to be provided to each of the pluralityof subsections 211-216. Furthermore, the determination of theappropriate voltage to provide to the subsections 211-216 can be carriedout dynamically to adjust the supply voltages provided to thesubsections of the display 210 in real time, and can be performed toadjust the supply voltage for each frame of a video signal.Implementations of the present disclosure also allow for adjusting thesupply voltage provided to each subsection at a frequency less than theframe rate of a video signal. For example, the display system 200 canallow for the supply voltage provided to the subsection 211 to be fixedat the same level for two or more sequential frames of a video beforebeing adjusted again.

The subsections 211-216 of the display 210 can also be referred to asregions or portions of the display. In some embodiments, the subsections211-216 can be non-overlapping subsections. In the exemplaryconfiguration illustrated in FIG. 2, the subsections 211-216 span thewidth of the display 210. However aspects of the present disclosureapply to displays having subsections that encompass less than the widthof a display. In addition, aspects of the present disclosure apply todisplays with subsections that are not regularly or evenly spaced. Forexample, subsections of a display may be arranged such that eachsubsection of the display corresponds to a region of the display thatdisplays features of a graphical user interface. The separatesubsections can be highlighted (“selected”) according to user inputs toenable the user to, for example, navigate menus associated with thegraphical user interface. By separately controlling the power of eachsubsection (e.g., the sections 211-216) in such a display, the voltagesupplied to the subsections can be varied depending on whether therespective subsection is selected to be brightened or is deselected tobe subdued. For example, and as described in connection with FIG. 5, fora display on a mobile device that is adapted to display emails,iconographic menu items, and the like, subsections of the display can beseparately addressable to adjust the power drawn by highlighted(“selected”) subsections of the display.

Additionally, while FIG. 2 is illustrated with reference to adjustingthe positive supply voltage (i.e., Vdd₁, Vdd₂, etc.) to each subsectionof the display 210, it is understood that the display system 200 canalso be implemented while adjusting a negative supply voltage (such assupply voltages Vss₁, Vss₂, etc.) or by adjusting both a positive supplyvoltage and a negative supply voltage for each subsection 211-216 of thedisplay 210.

FIG. 3A illustrates a flow chart for an exemplary method of operating adisplay while decreasing the power consumption of the display. The flowchart of FIG. 3A is described with reference to FIG. 2 for examplepurposes. The controller 230 receives the digital data 232 (310). Thedigital data 232 is indicative of an image to be displayed on thedisplay 210. The controller 230 analyzes the received digital data 232to corresponding to a first plurality of pixels (320). The firstplurality of pixels can be, for example, the pixels in the subsection211, or can be the pixels in the entirety of the display 210. Thecontroller 230 then selects a supply voltage to be applied to the firstplurality of pixels based on the analyzed digital data (330). Aspreviously described, the selection of an appropriate supply voltage canbe performed based on a range of the luminance values for the pixels inthe display, on a maximum and/or minimum of such luminance values, on avoltage necessary to set the drive transistor in saturation mode, and/orbased on a total anticipated cumulative load to be drawn to supply thedesired luminance values, and can be carried out by using look uptables, threshold values, and/or formulas. The controller 230 then sendsthe control signals 234 to the adjustable voltage supply 240 such thatthe adjustable voltage supply 240 supplies the selected supply voltageto the first plurality of pixels (340).

FIG. 3B illustrates a flow chart for another exemplary method ofoperating a display. The flow chart in FIG. 3B is similar to the flowchart of FIG. 3A except that the blocks 320, 330, and 340 are carriedout for a plurality (n) of subsections of the display 210. Each of thesubsections includes a plurality of pixels. Thus, in addition toanalyzing the received digital data corresponding to the first pluralityof pixels (320), the controller 230 also analyzes the received digitaldata corresponding to the additional pluralities of pixels according tothe number of subsections in the display being operated. For example,with reference to the display 210 in FIG. 2, the received digital datais analyzed for the second through sixth subsections (212 to 216) inaddition to the first subsection 211. For a generic display, thereceived digital data is thus analyzed for each subsection of thedisplay through the “nth” plurality of pixels (320 n). Similarly, asupply voltage is selected to be applied to each subsection of thedisplay through the “nth” plurality of pixels (330 n), and therespective selected supply voltages are supplied to each subsection inthe display through the “nth” plurality of pixels (340 n).

FIG. 4 illustrates a flowchart for another exemplary method of operatinga display. It is determined whether the display is operating in an idlemode (410). If the display is operating in an idle mode, portions(“subsections”) of the display are identified that are set to a darksetting during the idle mode (420). The supply voltage to the identifiedportions of the display are then turned off (430). Turning off thesupply voltage to the identified portions of the display preventscurrent from being conveyed through pixels in the identified portions.In addition, the programming operation of the identified portions of thedisplay can be ceased (440). Ceasing the programming operation in theidentified portions advantageously prevents the display from drawingpower during the programming operation. Without ceasing the programmingoperation, energy is generally expended during each frame to: addresseach row and provide programming voltages or programming currents via adata driver in order to charge a storage device within each pixel to alevel that will prevent the drive transistor from turning on such thatno light is emitted. In addition, for embodiments incorporatingmonitoring systems (such as the monitoring system 115 shown in FIG. 1A),the compensation and monitoring operation generally requires additionalpower to be drawn during monitoring and/or compensation operations ofthe display. In such implementations incorporating a monitoring system,the monitoring and compensation functions for the identified portions ofthe display that are set to a dark setting are advantageously ceasedduring the idle mode of the display. Once the programming, monitoring,and/or compensation operations are ceased for the identified portions ofthe display, an inquiry is made intermittently to check whether thedisplay remains in the idle mode (410).

FIG. 5 illustrates an example screen capture of a display of a list ofemails and incorporating selectable features. On the example screencapture shown in FIG. 5, an email with the subject line “Now Smell This”is operated according to a second positive supply voltage Vdd2. Forexample, where the “Now Smell This” email was highlighted relative toother emails listed, such as to indicate a user selection, the voltageof Vdd2 can be adjusted relative to the other voltage values (e.g., thevoltages Vdd3, Vdd4, Vdd5, Vdd6) such that the top email in the list canbe shown highlighted relative to the other emails listed without wastingenergy in the channel regions of the drive transistors in the pixelcircuits of the other sections of the display. In addition, a headermenu is separately controlled by the supply voltage Vdd1 such that theheader menu can be shown bright (such as to indicate selection) whileother sections of the display are shown subdued (“dimmed”).

The screen capture in FIG. 5 illustrates a display system for a phone orother mobile device that has been segmented into subsections that haveseparately adjustable supply voltages. In some embodiments, thesubsections coincide with regions on the graphical user interface thatare separately highlighted (e.g., highlighted and/or dimmed) to allow auser to navigate the user interface (e.g., the list of emails). Duringthe display of the list of emails shown by the screen capture in FIG. 5,Vdd2 can be set at a higher level than Vdd3-Vdd6 to allow the display inthe subsection indicated by Vdd2 to be brighter than the othersubsections of the display without unnecessarily wasting power in thedimmed regions.

FIG. 6A is an example screen capture of a display menu with selectablefeatures. FIG. 6B is another example screen capture of the screen shownin FIG. 6A, but with an additional highlighted region shown. The screencapture in FIGS. 6A and 6B is another example display of a graphicaluser interface for a mobile device, such as a phone, PDA, or similardevice. The graphical user interface illustrated in FIGS. 6A and 6Bpresents a menu of available programs and features on the device that isnavigated according to user inputs provided by a user of the device. Thevarious menu items on the display are indicated by iconographic symbolsand are arranged in rows coinciding with the separately adjustablesubsections of the display in FIGS. 6A and 6B. In particular, thesubsection (“region”) indicated by Vdd3 is highlighted relative to theadjacent subsections of the display. The icons in the highlightedsubsection therefore appear brightened (“highlighted”) relative to theicons in the adjacent subsections (e.g., the subsections indicated byVdd2, Vdd4, Vdd5, Vdd6), which are subdued. In operation of thegraphical user interface shown in FIGS. 6A and 6B, energy can be savedby decreasing the voltage supply (i.e., decreasing ΔV) provided to thedeselected subsections (e.g., the subsections indicated by Vdd2, Vdd4,Vdd5, Vdd6).

In addition, in comparing the screen shots in FIGS. 6A and 6B, thescreen shot in FIG. 6B shows the header bar in the region indicated byVdd1 in a highlighted state. By contrast, the header bar is in asubdued/dimmed state in FIG. 6A. It should be noted that the header barin FIGS. 6A and 6B is of a different size than the other subsections ofthe display, such as the subsection indicated by Vdd2, and the size ofthe segmented subsections of the display are selected to correspond tothe brightness-variable regions of the user interface shown on thedisplay. Thus, in some embodiments of the present disclosure displaypanels with segmented adjustable power supply regions are designed tohave sizes and/or shapes of distinct adjustable regions correspond tosizes and/or shapes of a user interface to be operated on the display.

To enable the highlighting of the header bar as shown in FIG. 6B, themagnitude of Vdd1, and thus the magnitude of ΔV, can be increasedrelative to the value of Vdd1 in FIG. 6A. In other words, to save energywhile the header bar is not highlighted, the magnitude of Vdd1 can bedecreased relative to the value of Vdd1 when the header bar ishighlighted. Advantageously, saving energy in the operation of thedisplays shown in FIGS. 5 through 6B allows the device to operate for alonger duration from a given battery charge. Furthermore, decreasing theamount of energy converted to heat energy in the channel regions of thedimmed regions of the display extends the lifetime of the display panelby decreasing the electrical degradation of the drive transistors withinthe pixels of the display.

FIG. 7 illustrates an example configuration for electrode patterning ofa display array 710 where supply lines are separately adjustable. Thedisplay array 710 includes a plurality of subsections arranged in agrid. Each of the subsections are separately controllable by supplylines (e.g., the supply lines 701, 702) which connect to an adjustablevoltage supply. The display array 710 illustrated in FIG. 7 has a fixedpositive voltage supply Vdd (not shown) and the negative voltages supplyVss(i, j) is separately controllable (“addressable”) via the pluralityof supply lines that are provided for each subsection in a one to oneratio. In some embodiments of the present disclosure, the supply linesfor the array of Vss(i, j) regions can be considered a passive powersupply matrix of the display 710. That is, by controlling the magnitudeof Vss(i, j), each subsection in the grid of subsections can bedynamically supplied with a selected value of ΔV which is appropriate tothe respective subsection based on the luminance values desired for therespective subsection as indicated by a digital data input.

FIG. 8 illustrates another example configuration for a pattern ofelectrodes in a display array 810 where supply lines are separatelyadjustable. The display array 810 also includes a plurality ofsubsections arranged in a grid. In the configuration of the displayarray 810, the positive supply voltage Vdd(i) is separately controllablealong the rows of the grid formed by the plurality of subsections, andthe negative supply voltage Vss(j) is separately controllable along thecolumns of the grid formed by the plurality of subsections. By adjustingVss(j) via the column terminal connectors (e.g., the connectors 802,804, etc.) and Vdd(i) the row terminal connectors (e.g., the connectors812, 814, etc.), the ΔV applied to each subsection in the grid ofsubsections is separately adjustable. The column terminal connectors andthe row terminal connectors are connected to an adjustable voltagesupply and are dynamically set to appropriate voltages according thesystems and methods described herein. In some embodiments, the firstpower supply lines (e.g., the power rails set to Vdd(i)) can be situatedgenerally on one side of a display substrate, running horizontally,while the second power supply lines (e.g., the power rails set toVss(j)) can be situated over the pixel circuits and/or on anencapsulation substrate, running vertically, such that the pixelcircuits in the display panel 810 are deposited between the Vdd and Vsspower rails.

In some embodiments, the sizes and arrangements of the subsections ofthe display arrays are selected to correspond to portions of a displaythat are selectively highlighted according to a graphical userinterface. For example, the selectable features shown in FIGS. 6A and 6B(i.e., the iconographic menu items) can be dimensioned so as to coincidewith separately adjustable subsections of a display that displays thegraphical user interface.

Systems utilizing the above described methods to dynamically adjust thesupply voltages supplied to a display can decrease the power consumed bysuch a display device by a substantial factor relative to conventionaldevices utilizing fixed supply voltage lines. Energy savings can beroughly 20% compared to conventional systems.

Two or more computing systems or devices may be substituted for any oneof the controllers described herein. Accordingly, principles andadvantages of distributed processing, such as redundancy, replication,and the like, also can be implemented, as desired, to increase therobustness and performance of controllers described herein.

The operation of the example determination methods and processesdescribed herein may be performed by machine readable instructions. Inthese examples, the machine readable instructions comprise an algorithmfor execution by: (a) a processor, (b) a controller, and/or (c) one ormore other suitable processing device(s). The algorithm may be embodiedin software stored on tangible media such as, for example, a flashmemory, a CD-ROM, a floppy disk, a hard drive, a digital video(versatile) disk (DVD), or other memory devices, but persons of ordinaryskill in the art will readily appreciate that the entire algorithmand/or parts thereof could alternatively be executed by a device otherthan a processor and/or embodied in firmware or dedicated hardware in awell known manner (e.g., it may be implemented by an applicationspecific integrated circuit (ASIC), a programmable logic device (PLD), afield programmable logic device (FPLD), a field programmable gate array(FPGA), discrete logic, etc.). For example, any or all of the componentsof the baseline data determination methods could be implemented bysoftware, hardware, and/or firmware. Also, some or all of the machinereadable instructions represented may be implemented manually.

While the device goes in standby, the display shows some basicinformation. In some of the wearable devices (e.g., smart watch orexercise band) the display shows some content all the time. The mainchallenge in this case is the power consumption associated with thedisplay. This power consumption includes both static power stemming fromthe backlight or the emissive device in the pixel and dynamic powerassociated with refreshing the display.

To reduce the static power, the brightness of the display can bereduced, or only a section of the display can be ON and the rest OFF (orat lower brightness). This also can help the dynamic power consumptionsince only a small section of the display needs to be programmed.

One example of a display with segmented Vdd is illustrated in FIG. 9,where only the 3^(rd) segment is ON during a standby mode. Therefore,only the content for the 3^(rd) segment needs to be transferred to thedisplay, and therefore both dynamic and static power consumption will bereduced by 80%.

For dynamic power consumption, one can reduce the refresh rate (framerate) of the display. However, if the content of the display is changingover time (e.g., a watch face) this content needs to be produced andtransferred to the display. As a result, part of the main system will beon and there will be power consumption associated with transferring datafrom the main system to the display, as illustrated in FIG. 10.

To eliminate the extra power consumption during the standby associatedwith transferring data between the main system and the display, somebasic functionality can be added to the display driver to produce therecursive changes in the content. In one example, the driver can havemultiple frame buffers that are pre-populated by the main system inadvance (for example, before going to the stand by, or during boot up orduring power up) and depending on different conditions, one of the framebuffers can be used to program the display. For example, a timer can beused to flip between the frame buffers (refer to FIG. 11). The mainissue in this case is that for some applications such as a watch face,there are many different combinations that will require significantlylarge memory to store them as full frame buffers.

In another example, the driver can have a few full frame buffers and theother partial frame buffers only store the changes applied to one fullframe buffer, based on certain conditions. For example, the handleposition in a watch face can be stored as the changes to the watch facein the partial frame buffers, while the watch face itself is stored inthe full frame buffer. An exemplary block diagram of a display with afull frame buffer and a partial frame buffer is illustrated in FIG. 12.Here, the content generator module selects a full frame buffer and apartial frame buffer based on some conditions; and it modifies the imagestored in the full frame buffer based on the information in the partialframe buffer. Also, one can use multiple full and partial frame buffersto create a new content.

In yet another example, the driver can perform some basic calculationsuch as moving an object by a trajectory. In this case, for differentconditions, some part of the image in the full frame buffers is movedbased on a trajectory or the object stored in the partial frame bufferis moved and the main frame buffer is modified by the new calculatedobject.

While particular embodiments and applications of the present inventionhave been illustrated and described, it is to be understood that theinvention is not limited to the precise construction and compositionsdisclosed herein and that various modifications, changes, and variationscan be apparent from the foregoing descriptions without departing fromthe spirit and scope of the invention as defined in the appended claims.

What is claimed is:
 1. A system for driving a display, the systemcomprising: a plurality of groups of pixel circuits arranged in anarray, each of said pixel circuits comprising a light emitting deviceand a driving transistor for conveying a driving current through thelight emitting device; a plurality of supply lines each coupled to atleast one of said groups of pixel circuits; a plurality of voltagesources each coupled to at least one of said plurality of supply lines;and a controller configured to determine when said display is to be in astandby mode and, when said display is in said standby mode, to reducethe voltage supplied to a selected one of said groups of pixel circuitsfor dimming the selected group of pixel circuits providing a region ofsubdued brightness, and to turn off the voltage supplied to other groupsof pixel circuits.
 2. The system of claim 1 in which said controller,during said standby mode, supplies only said selected one of said groupsof pixel circuits with digital data indicative of an amount of luminanceto be emitted from said pixel circuits.
 3. The system of claim 1 inwhich said controller is further configured to determine, based ondigital data indicative of an amount of luminance to be emitted from thepixel circuits in said selected one of said groups of pixel circuits, amagnitude of the reduction of the voltage supplied to the selected oneof said groups of pixel circuits.
 4. The system of claim 1 in which saidcontroller is further configured to determine a magnitude of thereduction of the voltage supplied to the selected one of said groups ofpixel circuits such that the voltage supplied to the selected one ofsaid groups of pixel circuits is sufficient to set driving transistorsin the pixel circuits of the selected one of said groups of pixelcircuits in a saturation mode.
 5. The system of claim 1 in which saidcontroller is further configured to determine a magnitude of thereduction of the voltage supplied to the selected one of said groups ofpixel circuits by evaluating the voltages required in each pixel circuitto operate light emitting devices according to measured or predictedaging information for each pixel circuit.
 6. The system of claim 1 inwhich said controller is configured to reduce the voltage supplied tothe selected one of said groups of pixel circuits by reducing a voltageof the voltage source coupled to the supply line of the plurality ofsupply lines which is coupled to the selected one of said groups ofpixel circuits.
 7. The system of claim 1, wherein the display is amobile device display, said selected one of said groups of pixelcircuits being associated with a distinct portion of the display onwhich a selected feature of a graphical user interface is positioned. 8.The system of claim 7, wherein the mobile device is a phone.
 9. A systemfor driving a display, the system comprising: a plurality of groups ofpixel circuits arranged in an array, each of said pixel circuitscomprising a light emitting device and a driving transistor forconveying a driving current through the light emitting device; aplurality of supply lines each coupled to at least one of said groups ofpixel circuits; a controller configured to determine when said displayis to be in a standby mode and, when said display is in said standbymode, to reduce the rate at which at least a selected one of said groupsof pixel circuits is supplied with digital data indicative of amounts ofluminance to be emitted by said pixel circuits during dimming of theselected group of pixel circuits providing a region of subduedbrightness.
 10. The system of claim 9 in which said controller, duringsaid standby mode, supplies only said selected one of said groups ofpixel circuits with digital data indicative of an amount of luminance tobe emitted from said pixel circuits.
 11. The system of claim 9 in whichsaid controller is further configured to determine, when said display isin said standby mode, to reduce the voltage supplied to the selected oneof said groups of pixel circuits and to turn off the voltage supplied tothe other pixels.
 12. The system of claim 11 in which said controller isfurther configured to determine, based on digital data indicative of anamount of luminance to be emitted from the pixel circuits in saidselected one of said groups of pixel circuits, a magnitude of thereduction of the voltage supplied to the selected one of said groups ofpixel circuits.
 13. The system of claim 11 in which said controller isfurther configured to determine a magnitude of the reduction of thevoltage supplied to the selected one of said groups of pixel circuitssuch that the voltage supplied to the selected one of said groups ofpixel circuits is sufficient to set driving transistors in the pixelcircuits of the selected one of said groups of pixel circuits in asaturation mode.
 14. The system of claim 11 in which said controller isfurther configured to determine a magnitude of the reduction of thevoltage supplied to the selected one of said groups of pixel circuits byevaluating the voltages required in each pixel circuit to operate lightemitting devices according to measured or predicted aging informationfor each pixel circuit.
 15. The system of claim 11 further comprising: aplurality of voltage sources each coupled to at least one of saidplurality of supply lines, in which said controller is configured toreduce the voltage supplied to the selected one of said groups of pixelcircuits by reducing a voltage of the voltage source coupled to thesupply line of the plurality of supply lines which is coupled to theselected one of said groups of pixel circuits.
 16. The system of claim11, wherein the display is a mobile device display, said selected one ofsaid groups of pixel circuits being associated with a distinct portionof the display on which a selected feature of a graphical user interfaceis positioned.
 17. The system of claim 16, wherein the mobile device isa phone.